class User:
    
    def __init__(self, first_name, last_name, age=0) -> None:
        self.first_name = first_name
        self.last_name = last_name
        self.age = age
        self.login_attempts = 0

    def describe_user(self):
        if self.age == 0:
            print(self.first_name, self.last_name)
        else:
            print(self.first_name, self.last_name, self.age)

    def greet_user(self):
        if self.age == 0:
            print(f"Hello {self.first_name} {self.last_name}!")
        else:
            print(f"Hello {self.first_name} {self.last_name}, {self.age} years old!")

    def increment_login_attempts(self):
        self.login_attempts += 1

    def reset_login_attempts(self):
        self.login_attempts = 0